1. Field of the Invention
The present invention relates to magnetic disk apparatus with high-density magnetic information recording performances and control methodology thereof.
2. Description of the Related Art
Conventionally known magnetic disk apparatus adaptable for use as external storage devices or else of computers are typically designed to include a rotation mechanism for driving more than one magnetic disk to rotate or spin at high speeds, and a magnetic head slider with a built-in recording/reproduction element. The magnetic head slider is supported by a load beam so that it is position-determined and placed along the diameter of the magnetic disk. The magnetic disk apparatus is arranged to record magnetic information at a desired track(s) on the magnetic disk and also reproduce such stored magnetic information out of the magnetic disk while letting the magnetic head slider relatively move over the magnetic disk. The magnetic head slider is designed to use an air lubrication shaft bearing for flotation by wedge film effects of the air. The use of such structure precludes any direct physical contact between the magnetic disk and magnetic head slider.
In addition, typically employable methodology for achieving higher recording densities and larger storage capacities of magnetic disk apparatus with or without reducing the size and shape thereof includes methods of increasing track densities and methods of increasing on-track linear recording densities. The on-track linear record density increasing methods may in turn include, but not limited to, a method for increasing the sensitivity of a recording/reproduction element used, and a method of reducing the distance between the record/reproduction element and its associative record carrier body, also known as recording medium. One typical approach to effectively achieving the latter method is to reduce the distance between a magnetic head slider and magnetic disk, that is, the flying height of such slider.
On the other hand, traditionally in cases where the flotation amount of the magnetic head slider is designed, there are provided certain margins which are determined by taking into account of any possible flotation amount reduction occurring due to machining variation of the magnetic head slider and/or environmental differences such as atmospheric pressure differences. If such margins are removed away, then it is possible to further shrink the resultant flotation amount of the record/reproduction element.
A converter for use in recording devices capable of individually precise or micro-adjusting the distance between a recording/reproduction element and a magnetic disk has been disclosed in JP-A-62-250570. The converter as taught thereby is arranged so that a built-in miniaturized or micro actuator is mounted at part of the magnetic head slider, which actuator is generally formed of more than one piezoelectric element. Assembling such piezoelectric micro-actuator enables accomplishment of individual micro-adjustability of the distance between the record/reproduction element and the magnetic disk.
The scheme for controlling the flotation amount of such record/reproduction element using the microactuator as recited in the above-identified Japanese document is generally called the active head slider scheme. This document also suggests therein another method for using the actuator piezoelectric element also as a sensor for detection of contact between the record/reproduction element and magnetic disk.
Another prior art method is available for designing a magnetic resistive element making up a magnetic information reproduction element in such a way that it also do double-duty as a contact detection sensor, as has been recited in JP-A-10-233070. This method makes use of a technique for detecting a change in resistivity occurring due to a temperature variation upon contacting, also known as thermal asperity, in a way independent of standard or ordinary magnetic information read/write sessions.
On the other hand, in order to meet the need for achievement of higher recording densities of information, it should be required to further reduce the distance between the record/reproduction element and the magnetic disk. This in turn strictly requires that design be made within a specific flotation amount region in which intermittent physical contact takes place due to micro-unevenness configuration on the magnetic disk side and also on the magnetic head slider side.
Additionally, from a view point of preclusion of the magnetic head slider's unwanted vibration due to physical contact and prevention of thermal asperity, a need is felt to minimize the frequency of physical contact events and the volume of an impingement or collision portion. Due to this, it is required that the magnetic head slider be designed to have its flotation amount that is set at a carefully selected level or greater. Accordingly, the wideness of an allowable region that is limited by upper and lower limit values of the flotation amount is presently made further narrower than was used conventionally.
Unfortunately, with the active head slider scheme as taught from the above-identified former Japanese citation JP-A-62-250570, it is required in order to attain the required high record density to further shrink the distance between the record/reproduction element and the magnetic disk, although the scheme offers enhanced effectivities for reduction of the distance between the record/reproduction element and magnetic disk.
As per the method for detecting a resistance change occurring due to a temperature variation upon contacting, i.e. thermal asperity, independently of ordinary magnetic data read/write operations as suggested by the latter document JP-A-10-233070, this method is encountered with a risk of frequent occurrence of intermittent physical contact due to microconfiguration on the magnetic disk side and on the magnetic head slider side, causing a serious problem as to likewise decreases in durability and reliability.